Water activity (a_w) refers to “free” water available for microbial growth. For microbial growth to occur, moisture must be freely available. The water activity of a material determines which types of mold would grow on that material.

Technically, the water activity is defined as the ratio of the vapour pressure exerted by the water in the material to the vapour pressure of pure water at the same temperature and pressure. Check out our Mold Inspection, Identification and Control course to learn more about Water Activity. 

Types of Mold based on Water Activity

Indoor molds vary in their water activity requirements and this ranges from 0.7 to >0.9. Higher a_w materials tend to support the growth of more microorganisms. Unlike molds, bacteria usually require a water activity of at least 0.91 a_w. Molds can be grouped according to their moisture requirements as follows:

• Extremely to moderately xerophilic. These molds are the primary colonisers and they are capable of growth below 0.8 a_w. Examples include Aspergillus and Penicillium
• Slightly xerophilic. These molds are the secondary or intermediate colonisers. They are capable of growth between 0.8 and 0.9 a_w. Examples of molds in this category include Altemaria and Cladosporium
• Hydrophilic. Molds in this category are tertiary colonisers and require at least 0.9 a_w for growth. Such high water activity can only be achieved through water intrusion and to a lesser extent high humidity and condensation. Examples of hydrophilic molds include Stachybotrys and Chaetomium

Check out our Mold Inspection, Identification and Control course to learn more about Types of Mold.

Note:

1. Xerophilic means “dry loving.” Thus, xerophilic molds are those that can or prefer to grow in “dry” environments. “Dry” is used here in relative sense since no mold can grow in a completely dry environment.
2. Hydrophilic means “water loving.” Thus, hydrophilic molds are those molds that require very high levels of moisture to grow.

Indicators of Water Damage

Water damage may occur over many months, mainly through roof leakage, but also via rising damp and defective plumbing, which result in mold growth. Indoor molds as well as bacteria are usually saprophytic, meaning that they obtain nutrients from dead organic matter. The nutrients are from the breakdown of simple to complex sugars such as starches, cellulose and pectin. The materials most susceptible to mold growth are organic materials containing cellulose (i.e. jute, wallpaper, cardboard and wooden materials). The tertiary colonisers are used as the indicators of moisture damage. The table below shows some of the most common indicators of water damage in buildings.

Indicators of excessive moisture or chronic condensation

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Health effects associated with Aspergillus fumigatus

The spores of Aspergillus fumigatus are very small. Having a diameter of 2–3.5 µm, they are easily inhaled deep into the lungs. It is estimated that people inhale at least several hundreds of spores of Aspergillus fumigatus per day without harm. However, Aspergillus fumigatus is an opportunist pathogen (Hazard Risk Group 2) and can cause a lung infection (aspergillosis), in people with weak immune system. Most of the cases of aspergillosis are caused by this fungus. Because of its potential role as an opportunist pathogen, there is concern about high concentrations of Aspergillus fumigatus spores in the vicinity of hospitals, where those with compromised immune system such as organ transplant and cancer patients, may be at increased risk of infection. Therefore, monitoring for airborne spores in hospitals especially during renovations is a good practice.

Occurrence of Aspergillus fumigatus

Aspergillus fumigatus naturally occurs in decaying organic material, but because it is a thermotolerant fungus it grows well at raised temperatures experienced during the composting process. Within the indoor environment, A. fumigatus belongs to the group of indicator microorganisms typical of moisture-damaged buildings such Stachybotrys, Chaetomium, Fusarium and Ulocladium. The following characteristics make A. fumigatus a ubiquitous opportunistic pathogen: 1) ability to survive and grow in a wide range of environmental conditions, 2) effective dispersal in the air, 3) physical characteristics that allow spores to reach deep into the respiratory system, and 4) ability to swiftly adapt to the host environment.

Air Sampling for Aspergillus fumigatus

In hospital environment, air sampling may be conducted to monitor air quality during construction, to verify filter efficiency, or to commission new space prior to occupancy. Because aspergillosis cases have occurred when airborne fungal spore concentrations ranged as low as 0.9–2.2 colony-forming units per cubic meter (CFU/m³) of air, it is suggested that an air volume of at least 1000 L (1 m³) should be considered when sampling highly filtered areas.

Sampling media and incubation temperature for Aspergillus fumigatus

Malt extract agar (MEA) can be used to sample for Aspergillus fumigatus. For selective isolation of A. fumigatus, a high incubation temperature of 37 to 40 is then used as this inhibits growth of other saprophytic fungi.

References

1. Kwon-Chung, K. J., & Sugui, J. A., 2013. Aspergillus fumigatus—What Makes the Species a Ubiquitous Human Fungal Pathogen? PLoS Pathogens, 9(12), e1003743. http://doi.org/10.1371/journal.ppat.1003743
2. Sehulster, L. et al., 2003. Guidelines for environmental infection control in health-care facilities. Morbidity and Mortality Weekly Report Recommendations and Reports RR, 52(10).
3. Swan, J. et al., 2003. Occupational and environmental exposure to bioaerosols from composts and potential health effects: a critical review of published data, HSE Books.
4. Streifel, A. et al., 1983. Aspergillus fumigatus and other thermotolerant fungi generated by hospital building demolition. Applied and environmental microbiology, 46(2), pp.375–378.

Health Effects Associated With Mold Spores

Mold spores are common in household and workplace dust. Also, due to their light weight, mold spores are often floating in the air both outdoors and indoors. Inhaling mold spores may cause allergic reactions in sensitive individuals. Allergic responses include hay fever-type symptoms, such as sneezing, runny nose, red eyes, and skin rash (dermatitis). Allergic reactions to mold spores are common. They can be immediate or delayed. Mold spores can also cause asthma attacks in people with asthma who are allergic to mold.

We breathe in mold spores and fragments every day, indoors and outdoors. Usually these exposures do not present a health risk. However, health problems may result when people are exposed to large amounts of mold, particularly indoors.

In about 20 percent of people, the immune system overreacts and causes the allergic response resulting in symptoms such as runny nose, scratchy throat and sneezing. Most of us know this allergic illness as “hay fever” or “allergic rhinitis.”

If you have an allergy that never ends when seasons change, you may be allergic to mold spores. Allergic symptoms from outdoor mold spores are most common in summer.

How do I get rid of mold spores

It is impossible to get rid of all mold spores indoors; some spores will be found floating through the air and in house dust. However we can reduce the amount of spores in our homes by controlling mold growth. The mold spores will not grow if moisture is not present. Therefore, indoor mold growth can and should be prevented or controlled by controlling moisture indoors. If there is no mold growth indoors then the only source of spores would be outdoors. Spores originating from outdoors may not be in amounts that would present a health problem. If there is mold growth in your home, you must clean up the mold and fix the water problem. If you clean up the mold, but don’t fix the water problem, then, most likely, the mold problem will come back.

Common Allergy Causing Mold Spores

Although there are many types of molds, only a few dozen are known to cause allergic reactions. Alternaria, Cladosporium, Aspergillus, Penicillium, Helminthosporium, Epicoccum, Fusarium, Mucor, Rhizopus and Aureobasidium are the major culprits. Some common mold spores can be identified easily in a laboratory when viewed under a microscope.

Mold spores Release

The spores can be actively released or passively released depending on the type of mold. The release of spores is also influenced by environmental conditions. Some spores are released in dry, windy weather. Others are released with the fog or dew when humidity is high.

Air Sampling For Mold Spores

Indoor air sampling for mold is important for several reasons. Mold spores are not visible to the naked eye and the only way to determine whether the air is contaminated and the types of mold present is through laboratory analysis of the air samples. Having air samples analyzed can also help provide evidence of the scope and severity of a mold problem, as well as aid in assessing human exposure to mold. After mold removal, new samples are typically taken to help ensure that the amount of airborne mold spores has been successfully reduced.

Air samples can be used to gather data about mold present in the interior of a house. Samples are taken using a pump that forces air through a collection device which catches mold spores. The sample is then sent off to a laboratory to be analyzed.

Common Building Molds (also called Mildew or Black Mold) and Their Associated Health Effects

People often talk of black mold or mildew in their bathroom, ceiling, basement and kitchen.

The question you may ask, is it a single type of mold? No. In most cases, more than one type of mold will be growing on the same surface. At least 150 mold species have been reported from residential and commercial buildings. Fortunately, not all of these are harmful to most people, so even if you suspect mold growth, don’t panic; but make you have it tested at the earliest.

If you want to know more about specific molds, visit the Mold Library.

If you are looking for a professional to help you with mold testing or remediation, contact us to discuss your situation further.

What Are the Health Effects Of Indoor Mold?

Exposure to indoor mold has been associated with the following health problems:

• Lower respiratory symptoms such as coughing and wheezing
• Respiratory infections such as aspergilloses
• Allergic diseases, including allergic asthma and bronchitis
• Non-inflammatory, unspecific symptoms, such as eye and skin irritation, fatigue, headache, nausea, and vomiting

Which Molds and Why Do They Grow Indoors?

The level of moisture (usually referred to as water activity) in building material determines not only whether mold will grow or not but also the types that colonize the material. Damp materials with a water activity value equal to or greater than 0.90 are usually colonized by strains of Aspergillus fumigatus, Trichoderma spp., Exophiala spp., Stachybotrys spp., Phialophora spp., Fusarium spp., Ulocladium spp., and yeasts such as Rhodotorula spp.

Materials with a water activity value ranging from 0.90 – 0.85 are colonized by Aspergillus versicolor while those with water activity values of 0.85 or slightly less are colonized by Aspergillus versicolor, Eurotium spp., Wallemia spp., and Penicillium spp., such as Penicillium chrysogenum and Penicillium aurantiogriseum.

A study conducted in Denmark found that water leakage through roofs, rising damp, and defective plumbing installations were the main sources for water damage with subsequent mold growth.

The building materials most susceptible to mold attacks were water damaged, aged organic cellulose containing materials such as wood, jute, wallpaper, and cardboard. In this study, the molds that were most frequently encountered were Penicillium (68%), Aspergillus (56%), Chaetomium (22%), Ulocladium (21%), Stachybotrys (19%), Cladosporium (15%), Acremonium (14%), Mucor (14%), Paecilomyces (10%), Alternaria (8%), Verticillium (8%), and Trichoderma (7%). These molds are all known to cause different types of inhalation allergy. The species most frequently encountered were Stachybotrys chartarum, Penicillium chrysogenum, and Aspergillus versicolor.

If you’re interested in learning more about mold and bacteria, you can explore the links above to the left. If you’re curious or concerned about anything not covered here, please use the Question Form.

Interested in having an in-depth understanding? Check our Resources page which will provide you with links to other educational materials.

Metalworking fluids (MWF) is the name given to a range of oils (mineral -petroleum, animal, marine, vegetable or synthetic oils) and other liquids that are used to cool and/or lubricate metal works during machining, grinding, cutting, milling, etc. There are four basic classes of Metalworking Fluids:

• Straight Oils: Also called "cutting" or "neat" oils.
• Soluble Oils: This category contains 30 to 85% severely refined petroleum oils, as well as emulsifiers to disperse the oil in water.
• Semi-synthetic fluids: These contain 5 to 30% severely refined petroleum oils, 30 to 50% water and a number of additives.
• Synthetic fluids: These do not contain petroleum oils. Instead, they use detergent-like components and other additives

Although each class will vary greatly in composition, each may contain additives such as sulphurized or chlorinated compounds, corrosion inhibitors, extreme pressure additives, emulsifiers, biocides, stabilizers, dispersants, defoamers, colorants, dyes, odorants and fragrances.

Why test for bacterial or fungal contamination of Metalworking fluids?

Although metalworking fluids are used throughout the industry by hundreds of thousands of workers safely, problems can develop when good hygiene practices are not followed or when fluids are not properly managed or maintained.

Bacterial and fungal contamination of metalworking Fluids (MWFs) is a major concern in the industries which use these fluids. It may cause equipment malfunction, off-odors, degradation in the fluid quality, economic losses and finally, they pose as a major health hazard. Several Gram +ve and Gram -ve bacteria are found as contaminants. These include Staphylococcus sp., Bacillus sp., Pseudomonas sp., Proteus sp. and Coliforms. Amongst the fungi, Aspergillus sp., Penicillium sp., Fusarium sp. and Cephalosporium sp. are found to be prevalent.

What are the health concerns?

Major health concerns of improperly managed Metalworking fluids include skin irritation, allergic contact dermatitis, irritation of the eyes, nose and throat, and, occasionally, breathing difficulties such as bronchitis and asthma. There is also evidence that some MWFs are associated with an increase in risk of certain cancers such as larynx, rectum, pancreas and skin.

What are the possible sources of contamination?

Most bacteria and fungi enter the system through the water supply, debris and build up in any equipment like hoppers, conveyors and sump pump. Therefore, it is highly recommended by experts to perform monitoring of metalworking fluids, associated machinery and pipe work, periodically, to ensure quality and safety.

What can MBL do for you?

At MBL, we perform total mould and bacterial counts of the samples to help you monitor quality standards of MWFs. MBL provides you with a Report of Analysis that indicates levels of mold and/or bacterial contamination and what can be regarded as good, reasonable or poor standards of fluid management.

Following are the acceptable indicator levels used to determine the standard of the fluids and required action:

• < 10³ CFU/mL: Good control. Bacteria are being maintained at low levels. No further action is required;
• 10³ to < 10⁶ CFU/mL: Reasonable control. Review control measures to ensure levels of bacteria remain under control. Risk assessment should specify action to be taken. Biocides and or cleaning may be indicated. If biocides are used, expert advice should be obtained, and the concentration of biocides should be monitored
• > 10⁶ CFU/mL: Poor control. Immediate action should be taken in line with the risk assessment. Normally at very high levels draining and cleaning, should take place.

Comparing your counts with these levels will help you decide the quality of your metal working fluid. It will also help you select the treatment method if contamination is detected and economize performance.

Should you have a question concerning contamination of metalworking fluids or our services contact us via email, or fill out our Question Form and submit for priority attention. Your questions will be answered within 48-72 hours. For immediate assistance call 905-290-9101.

Building molds and yeasts such as strains of Aspergillus fumigatus, Trichoderma spp., Exophiala spp., Stachybotrys spp., Phialophora spp., Fusarium spp., Ulocladium spp., and yeasts such as Rhodotorula spp. grow well on very wet building materials.

Materials with a water activity value ranging from 0.90 – 0.85 are colonized by Aspergillus versicolor while those with water activity values of 0.85 or slightly less are colonized by Aspergillus versicolor, Eurotium spp., Wallemia spp., and Penicillium spp., such as Penicillium chrysogenum and Penicillium aurantiogriseum.

Hazard Classes of Building Molds

In some countries building molds have been grouped into 3 hazard classes based on associated health risk. These classes are similar to risk groups assigned to microorganisms handled in laboratory environments.

• Hazard Class A: includes fungi or their metabolic products that are highly hazardous to health. These fungi or metabolites should not be present in occupied dwellings. Presence of these fungi in occupied building requires immediate attention.
• Hazard class B: includes those fungi which may cause allergic reactions to occupants if present indoors over a long period.
• Hazard Class C: includes fungi not known to be a hazard to health. Growth of these fungi indoors, however, may cause economic damage and therefore should not be allowed.

See which hazard class each of the common building molds belong to at Common Indoor Molds.

Is Sampling and Testing for Building Molds Necessary?

Yes. Building occupants need assurances that they were not exposed to building molds that may cause health problems. Some of the objectives for laboratory testing are:

• To determine which moulds are growing in the building and hence the level of protection required for both the occupants and remediation staff.
• To determine the presence/absence of airborne spores, their composition and concentrations in situations where occupants complain of mould related ill health but with no obvious visible mould growth.
• To determine if spores from visible growth sources had become airborne.
• To detect and quantify certain mould species.
• To determine the effectiveness of remediation work.

References

Gravesen S, Nielsen PA, Iversen R, Nielsen KF. (1999). Microfungal Contamination of Damp Buildings–Examples of Risk Constructions and Risk Materials. Environmental Health Perspectives, Supplements Volume 107, Suppl 3:505-8.

Sedlbauer, K., (2002): Prediction of mould fungus formation on the surface of and inside building components. Doctoral Dissertation, Fraunhofer Institute for Building Physics.

“Eating mouldy bread is discouraged. Where can I find the facts that prove this? Are there moulds that grow on bread that are harmless? Some of my patients that survived food shortages in The UK during World War II by eating mouldy bread and other foods insist that such fears about mould are unfounded”.

Those are the comments/questions that we received and below we explain why eating mouldy food should be discouraged.

Why is eating mouldy food discouraged?

It is true that people may eat mouldy food without any harm. In many cases, children and adults who live on the streets in developing countries survive on food and fruits thrown into waste bins. Most of these foods and fruits are usually contaminated with mould and bacteria.

The major reasons why eating mouldy food is dangerous is because such food is likely to be contaminated with mycotoxins (i.e., fungal poisons).

Luckily, moulds that produce toxins (also called toxigenic moulds) require certain growth conditions to produce the toxins and hence presence of these moulds on food does not necessarily mean the food contains mycotoxins.

There is also a high risk of food poisoning caused by bacteria such as Staphylococcus aureus, Salmonella, Clostridium perfringens, Campylobacter, Listeria monocytogenes, Vibrio parahaemolyticus, Bacillus cereus, and Entero-pathogenic Escherichia coli.

Mycotoxin poisoning is primarily through ingestion and to some extent through contact. The effect of poisoning by mycotoxin is called mycotoxicoses. There are several documented (and probably more undocumented) cases of mycotoxicoses both in human and domesticated animals.

• The first documented major outbreak of gangrenous ergotism is suspected to have occurred in the Rhine Valley, in 857 A.D. Numerous epidemics of ergotism followed with thousands dying as a result of the continual consumption of infected rye. Children were often the most susceptible victims.
• In 1913, a food – borne disease called alimentary toxic aleukia occurred in Siberia. Several larger outbreaks occurred during the war years of 1941-1945 involving several districts in Western Siberia and European Soviet Russia. The disease claimed at least 100,000 people. The disease was attributed to the consumption of bread made from wheat contaminated with trichothecene mycotoxins produced by Fusarium sporotrichioides and Fusarium poae.

  

• In the 1930s in Ukraine and other parts of Eastern Europe there were outbreaks of mycotoxicoses in horses and other animals fed with hay and feed contaminated with Stachybotrys chartarum. Stachybotrys chartarum produces satratoxins (L, D, F, G and H), a class of trichothecenes which are potent inhibitors of protein synthesis in mammalian cells. Affected animals exhibited symptoms that included irritation of the mouth, throat, and nose; shock; dermal necrosis; a decrease in leukocytes; hemorrhage; nervous disorder; and death. The condition was named stachybotryotoxicosis. Stachybotryotoxicosis has also been reported in farm workers who handled contaminated hay.
• In 1960, in England, about 100,000 turkeys and several other domestic birds died of aflatoxicosis (aflatoxin poisoning) after feeding on oil cake feed contaminated with aflatoxin, a highly potent mycotoxin produced by Aspergillus flavus and Aspergillus parasiticus.
• In South Africa in 1970 there was an outbreak of a disease condition called equine leukoencephalomalacia after horses were fed with mouldy corn contaminated with Fusarium verticillioides. This outbreak led to the discovery of a class of mycotoxins known as fumonisins.
• In 1974 an outbreak of aflatoxicosis in western India resulted in 397 recognized cases and 106 deaths.
• In the summer of 1987 in India, an outbreak of gastrointestinal disorder affected thousands of residents of Srinagar and the surrounding areas in the Kashmir Valley after consuming wheat that was contaminated with both Aspergillus and Fusarium species.
• In Kenya, in 2004 several people were hospitalized, and 125 of them died, after eating maize contaminated with Aspergillus flavus. The outbreak resulted from widespread aflatoxin contamination of locally grown maize, which occurred during storage of the maize under damp conditions.

Are there moulds that grow on food that are harmless?

Yes. In fact some moulds are used in the processing of food especially in Asian countries. The following are some of the moulds used in processing of foods.

• Penicillium camembertii and Penicillium roquefortii are used in the production of Camembert and Roquefort types of cheese respectively.

• Fusarium venenatum is used in the production of Quorn. Quorn is a mycoprotein (fungal protein) containing 12% protein and is used as an alternative to meat products. It contains no animal fat and cholesterol.

• Rhizopus oligosporous. Rhizopus oligosporous is used in the production of tempeh. Tempeh is a fermented soya bean paste made by inoculating cooked soya beans with the mould Rhizopus oligosporous. This mould forms a mycelium holding the soya beans together and its extracellular proteases break down the bean protein making them digestible.

• Aspergillus oryzae. Aspergillus oryzaeis used in processing of a number of soybean products. These include:
  • Miso, a fermented condiment made from soya beans, grain (rice or barley), salt and water. Miso production involves steaming polished rice which is then inoculated with Aspergillus oryzae and left to ferment to give an end product called koji.
  • Hamanatto, a Japanese soybean product.
  • Ket-jap, an Indonesian soy sauce.

Conclusion

Feeding on food or feed contaminated with mould is risky and should be avoided at all times. Eating such food could result to food poisoning either due to mycotoxin or bacterial contamination or both.

In agriculture Fusarium is known to cause diseases of many economically important crop plants. Some species are known to colonize stored cereal grains not only causing losses but also producing mycotoxins such as trichothecenes, zearalenone, and fumonisins that are harmful to humans and animals(1, 3).

In the medical field, the species cause opportunistic infections of human eyes, skin or nails and may also cause systemic infections in individuals with weak immune system. The most important species as far as human infection is concerned are Fusarium solani, F. moniliforme (=Fusarium verticilloides), F. oxysporum and F. dimerum (1, 3). Fusarium solani is also allergenic and is occasionally found in indoor environments. It affects 4% of nasobronchial allergy patients (4).

Some of the infections attributed to some species of Fusarium are:

• Fusarium keratitis
• Onychomycosis (nail infection)
• Certain skin infections
• Fusarium osteomyelitis (bone and joint infections)
• Pneumonia

In the industrial environment, Fusarium species are known to contaminate industrial products such as pharmaceutical solutions or machine cooling fluids. Fusarium keratitis has been in the news as the cause of severe fungal eye infections through contamination of contact lens solution.

Sampling for Airborne Spores of Fusarium Species

Fusarium species do not grow well at low water activity levels and will usually colonize very damp or wet material, hence, presence of Fusarium in a building is an indication of a water problem. Fusarium may produce three types of spores: namely, macroconidia, microconidia, and chlamydospores (3).

The macro and microconidia are the most likely to become airborne, but since they are produced in wet form they do not easily become aerosolized unless the mould is completely dry. Indoor airborne spore counts for Fusarium are therefore rarely high. A few spores of this fungus indoors could be an indication of serious mould growth.

Airborne microconidia and chlamydospores are difficult to identify and for air samples analysed by direct microscopy, only the macroconidia of some species may be reported. It is therefore possible that Fusariumspores (especially the microconidia) are usually lumped together with other unidentified spores.

For viable samples it is important to note that desiccation affects viability of Fusarium spores and therefore a few colony forming units (CFUs) would also be an indication of a problem.

According to Health Canada, persistent presence of significant numbers of Fusarium species and other toxigenic moulds such as Stachybotrys chartarum, Aspergillus and Penicillium requires further investigation (2).

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References

1. Guarro, J., and J. Gene. 1992. Fusarium infections. Criteria for the identification of the responsible species. Mycoses 35:109-114
2. Health Canada (1995). Indoor Air Quality in Office Buildings: A Technical Guide. A Report of the Federal-Provincial Advisory Committee on Environmental and Occupational Health.
3. Nelson, P.E., Dignani, C.M., and Anaissie, E.J (1994). Taxonomy, Biology, and Clinical Aspects of Fusarium Species. Clinical Microbiology Reviews, 7(4): 479-504.
4. Verma J, Sridhara S, Singh BP, Pasha S, Gangal SV, Arora N. (2001). Fusarium solani major allergen peptide IV-1 binds IgE but does not release histamine. Clin. Exp Allergy, 31(6):920-927.

Ulocladium (you-low-clay-dee-um) is a genus of saprophytic, darkly pigmented fungi.  Ulocladium  species are cosmopolitan and are commonly found in the soil and on decaying herbaceous plants, paper, textiles, dung, emulsion paint, grasses, fibres and wood. 

In buildings, Ulocladium is commonly found in damp or wet areas such as bathrooms, kitchens and basements and around windows. It is frequently isolated from painted surfaces, damp wall finished with wallpaper or water based emulsion paint; floor and mattress dust. It grows on very wet walls and particleboard. Because of its high water requirements it is considered an excellent indicator of water damage.

Ulocladium has two known species; Ulocladium chartarum and U. botrytis.

U. chartarum is the species most commonly found in indoor environment. Its presence in indoor environment together with other molds such as Stachybotrys, Fusarium and Chaetomium is an indication of water damage.

Ulocladium has been reported to cause Type I (hay fever) allergy. There have been cases of U. chartarum causing skin surface and deep skin infections in immuno-suppressed patients. U. botrytis has no proven pathogenicity.

Alternaria (all-tur-nair’-ee-uh) is another dark-colored mold. Alternaria species are among the most abundant fungi. It’s very closely related to Ulocladium. Alternaria can cause allergic reactions. It’s common in dust, around windows, damp areas, in soil, on foodstuffs, textiles, and on plants.  Exposure to Alternaria can provoke respiratory and asthmatic symptoms in susceptible persons.

If this article was helpful, you may also benefit from reading our list of common household moulds.

Plant parasitic Fusarium causes wilting of many plants including crops such as tomatoes, bananas, sweet potatoes, pigeon peas, and pears. Some species of Fusarium are commonly isolated from seeds, especially those of cereals.

In addition, this common species of fungus can produce a number of different mycotoxins which include trichothecenes (T-2 toxin, HT-2 toxin, deoxynivalenol (DON) and nivalenol), zearalenone and fumonisins. The Fusarium species are probably the most prevalent toxin-producing fungi in the northern temperate regions and are commonly found on cereals grown in the temperate regions of America, Europe and Asia. These toxins have been shown to cause a variety of toxic effects in both experimental animals and livestock and are also suspected of causing toxicity in humans.

In indoor environments Fusarium species are generally found under very wet conditions. They are commonly isolated from carpet and mattress dust, damp walls, wallpaper, polyester polyurethane foam, humidifier pans and areas where stagnant water occurs in HVAC systems. Some species cause keratitis in humans, and infect eyes and finger nails. Fusarium species are also an inhalation hazard.

Fusarium culmorum

F. culmorum is soilborne and has a worldwide distribution. Indoors, it has been isolated from floor, carpet and mattress dust; damp wall and polyurethane foam.

Health Effects Associated With Fusarium culmorum

Fusarium culmorum is associated with allergy. It also produces vomitoxin, a trichothecene mycotoxin that causes a serious feed refusal and vomiting in animals fed contaminated feed.

Fusarium solani

F. solani is a soil borne fungus found indoors in carpet and mattress dust; damp walls, wallpaper; polyester polyurethane foam; insulating cotton in duct liner; water pipes and humidifiers.

Health Effects Associated With Fusarium solani

F. solani causes keratitis in humans. It is also associated with wounds and infections of the eyes and fingernails. It poses inhalation and deep skin (dermal) inoculation health risks to persons with weak immune systems. It also poses health risks related to major barrier breaks such as corneal perforation, major surgery, peritoneal or venous catheter presence, and injection drug use.

Fusarium verticillioides (fomerly called Fusarium moniliforme)

F. verticillioides is soilborne. Indoors, it is found on humidifier pans and other areas where stagnant water occurs in HVAC systems. Also found in mattress dust, and on damp walls.

Health Effects Associated With Fusarium verticillioides

F. verticillioides causes keratitis in humans and invasive mycoses in immunocompromised people. It poses inhalation and deep skin (dermal) inoculation health risks to persons with weak immune systems. F. verticillioides also poses health risks related to major barrier breaks such as corneal perforation, major surgery, peritoneal or venous catheter presence, and injection drug use.

You can learn more about our Fusarium mold testing service here.